The present invention concerns a decorative or protective strip for application to the body of an automative vehicle, or the like, and particularly to such a strip which is an enclosed, hollow blow molded unit with temperature compensation means built into it.
A blow molded strip has a bottom surface that is applied to the external surface of a vehicle or the like and a top surface which is spaced from the bottom surface and attached to it at their peripheral margins.
Blow molded protective or decorative strips are known from German Pat. No. 2,536,766 and its British counterpart No. 1,527,663, both by the inventer hereof. Blow molded strips have numerous advantages over strips manufactured by other methods. However, blow molded strips still have a major drawback when applied especially to the external surface of an automotive vehicle.
Automotive vehicles are exposed to a wide range of temperature variations. For example, the surface of the vehicle and of any strip applied to it is likely to become quite hot in the sunlight on a hot day. The strip, which is plastic, and the vehicle body, which is metal, have different coefficients of temperature expansion, and the temperature variations generate stresses which are likely to eventually cause the bottom surface of the strip to tear away from the vehicle body.
Variations which sometimes are found in the thickness of the walls of the decorative piece and the considerable temperature differences that are likely to arise as between the bottom surface of the strip, which is on the surface of the vehicle, and the top of the strip, which is spaced from the vehicle and faces outwardly, will cause the top or visible side of the decorative strip to expand or contract at different rates than the bottom or mounted side. Eventually, the side at the higher temperature may buckle and the mounted side of the strip may tear away from the side of the vehicle. The just described buckling will be more severe on decorative strips with a more convex cross section than on such strips with a flatter cross section.
Various alternative techniques have been tried for holding such decorative strips in place on the side of the vehicle. Attaching these strips using a number of closely aligned fasteners to mount the strips on the body of the vehicle, with the mounting deigned to absorb the mentioned expansion and contraction of the strip, have been tried. This effort, however, has only been partially successful, and then only when the strips were relatively thin. Cementing the bottom surface of the strip to the side of the vehicle has not been very successful, as the strips did not stay in place very long for the reasons discussed. Another aspect of the problem was the additional expense involved in materials required and in the assembly steps.
Above noted British Pat. No. 1,527,663 shows a strip with longitudinal grooves into the surface of the top of the strip. Being the inventor of that patent, the co-inventor hereof is also aware that these grooves are not corrugating depressions in the bottom of the strip. Those prior art strips have deformed due to temperature differentials between the top and the bottom of the strip and because of the different coefficients of expansion of the strip and the vehicle body. Such deformations have been great enough that the fastenings of the strip have yielded, e.g., the cement holding the strip in place has cracked, and the strip has popped off the surface.